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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-12-11 16:18:22 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2016-03-31 13:33:19 -0700 |
| commit | 41abcf321d447b9987f6b7d1a9bb65831e786daf (patch) | |
| tree | c3f7bd7dbdc17f15b228ee5f18cb283212d8b1dc /Documentation/RCU | |
| parent | 70946a44deec299ef54c0ec933e8d82ddd4bcc6a (diff) | |
| download | lwn-41abcf321d447b9987f6b7d1a9bb65831e786daf.tar.gz lwn-41abcf321d447b9987f6b7d1a9bb65831e786daf.zip | |
documentation: Add real-time requirements from CPU-bound workloads
This commit records RCU's responsibility to avoid degrading latencies
of CPUs running tight loops within properly configured workloads,
both in kernel and in userspace.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'Documentation/RCU')
| -rw-r--r-- | Documentation/RCU/Design/Requirements/Requirements.html | 10 | ||||
| -rw-r--r-- | Documentation/RCU/Design/Requirements/Requirements.htmlx | 8 |
2 files changed, 17 insertions, 1 deletions
diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html index a725f9900ec8..3004baa71bcc 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.html +++ b/Documentation/RCU/Design/Requirements/Requirements.html @@ -1,5 +1,5 @@ <!-- DO NOT HAND EDIT. --> -<!-- Instead, edit Documentation/RCU/Design/Requirements/Requirements.htmlx and run 'sh htmlqqz.sh Documentation/RCU/Design/Requirements/Requirements' --> +<!-- Instead, edit Requirements.htmlx and run 'sh htmlqqz.sh Requirements' --> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> @@ -2171,6 +2171,14 @@ This real-time requirement motivated the grace-period kthread, which also simplified handling of a number of race conditions. <p> +RCU must avoid degrading real-time response for CPU-bound threads, whether +executing in usermode (which is one use case for +<tt>CONFIG_NO_HZ_FULL=y</tt>) or in the kernel. +That said, CPU-bound loops in the kernel must execute +<tt>cond_resched_rcu_qs()</tt> at least once per few tens of milliseconds +in order to avoid receiving an IPI from RCU. + +<p> Finally, RCU's status as a synchronization primitive means that any RCU failure can result in arbitrary memory corruption that can be extremely difficult to debug. diff --git a/Documentation/RCU/Design/Requirements/Requirements.htmlx b/Documentation/RCU/Design/Requirements/Requirements.htmlx index 3a97ba490c42..61caffc86823 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.htmlx +++ b/Documentation/RCU/Design/Requirements/Requirements.htmlx @@ -2338,6 +2338,14 @@ This real-time requirement motivated the grace-period kthread, which also simplified handling of a number of race conditions. <p> +RCU must avoid degrading real-time response for CPU-bound threads, whether +executing in usermode (which is one use case for +<tt>CONFIG_NO_HZ_FULL=y</tt>) or in the kernel. +That said, CPU-bound loops in the kernel must execute +<tt>cond_resched_rcu_qs()</tt> at least once per few tens of milliseconds +in order to avoid receiving an IPI from RCU. + +<p> Finally, RCU's status as a synchronization primitive means that any RCU failure can result in arbitrary memory corruption that can be extremely difficult to debug. |